A method for continuous operation of prolific and medium range producing oil wells by means of electrically-powered submersible centrifugal pumping units (EPSCPUs) with uncontrollable electrical drives is known (Bogdanov, A. A. Submersible Centrifugal Electric Pumps. Moscow, Costoptekhizdat, 1957, p.p. 8-11).
The disadvantage of the method is high electric power consumption caused by the need to control the delivery of a downhole submersible pump delivery by throttling (Bogdanov, A. A. Submersible Centrifugal Electric Pumps. Moscow, Costoptekhizdat, 1957, p.p. 77-79). When medium production rate wells, that is, wells having the a liquid production rate of from 20 m3/day to 80 m3/day, are operated, the electric power consumption increases because of low efficiency values of electrically-powered submersible centrifugal pumps (EPSCPs) within the present delivery range (Ageev, Sh. R., Druzhinin, E. Yu. Approaches to Increasing Technical Level of OJSC ALNAS Stages. Report at the XII-th All-Russian Technical Conference “Manufacture & Operation of Submersible Electric Pump Units,” Almetyevsk, Sep. 27-30, 2004, p.p. 5-6, 9-14). The increased electric power consumption results in reduction of the oil production profitableness.
A method for continuous operation of producing prolific wells by means of an EPSCPU with a controllable electrical drive is known (Ivanovsky, V. N. Maximum and Minimum Allowable EPSPCU Rotor Rotating Frequencies while Adjusting Production Capacity for Frequency Converters. Report at the XII-th All-Russian Technical Conference “Manufacture & Operation of Submersible Electric Pump Units,”” Almetyevsk, Sep. 27-30, 2004). The method consists in controlling the production unit capacity by changing an EPSCP rotation speed using change of a frequency of the alternating current (AC) powering a submersible electric motor (SEM).
The disadvantage of the method is the high cost of the equipment. The most expensive equipments are control stations (CSs) with frequency converters (FCs) for EPSCPUs. Because of their high costs, the CSs with FCs are used generally in prolific wells where capital expenditures are compensated within acceptable periods of time. Use of the CSs with the FCs in the medium production rate wells is usually unprofitable.
A method for periodical operation of producing stripper wells by means of an EPSCPUs with controllable electrical drives is known, said method comprising alternated pumping a liquid out of a well and accumulating the liquid in the well (RU 2,119,578). An aspect of the present method is that the EPSCPUs are not turned off during accumulation of the liquid in the well while operation continues at a reduced rotation speed so as to maintain a maximum EPSCP head at which a delivery is absent. The EPSCP head is not controlled by changing the rotation speed when pumping the liquid from the well. The prior art method is used in case if a check valve of an EPSCPU is not hermetical.
The disadvantages of the method are the low profitability of oil production caused by the high cost of the equipment because the latter comprises CSs with FCs, the high specific electric power consumption because the EPSCPU operates for the most of time at zero capacity, and small values of the time between overhauls caused by non-optimal working modes of the equipment and bad cooling conditions for the most time.
The closest prior art analogue taken as a prototype for the invention is a method for periodical operation of stripper and medium range producing wells by electrically-powered submersible centrifugal pumping units with uncontrollable electrical drives (Bogdanov, A. A. Submersible Centrifugal Electric Pumps. Moscow, Costoptekhizdat, 1957, p.p. 126, 128-130), said method comprising alternated pumping a liquid out of a well and accumulating the liquid in the well when the unit is turned off. The average capacity of the unit is controlled by changing a proportion between a liquid pumping-out-of-well duration and a liquid accumulation-in-well duration.
The disadvantage of the method is that placement of a well to periodical operation is always associated with loss of a certain oil amount as compared to an amount that could be produced in continuous operation (Schurov, V. I. Technology and Equipment of Oil Production. Moscow, Nedra, 1983, p.p. 412-417).
Further, increase of the number of EPSCPU starts in periodic well operation as compared to continuous operation and increase of a frequency of acting the relevant electrical, mechanical and hydraulic starting overloads result in reduction of the time between overhauls and the service life of the producing unit (Ivanovsky, V. N. Maximum and Minimum Allowable EPSPCU Rotor Rotating Frequencies while Adjusting Production Capacity for Frequency Converters. Report at the XII-th All-Russian Technical Conference “Manufacture & Operation of Submersible Electric Pump Units,” Almetyevsk, September 27-30, 2004, p. 1).
Reduction of oil production volumes and reduction of the time between equipment overhauls result in reduction of the oil production profitability.